Edit UI: more package updates + cleanup

In some recent tickers, Edit UI was updated from Vuex to Pinia.

In THIS ticket, a number of other packages need to be updated (partly to stay up to date with evolving packages and partly in preparation for Vue3). See [PR 540](https://github.com/bcgov/business-create-ui/pull/540) for a similar change made in Create UI.

To do:
- [ ] ~`array-move` instead of `array.prototype.move` if used~ _not used_
- [x] `lodash.omit` if used
- [ ] `pdfjs-dist` (plus update code that uses it)
- [ ] additional `@types/`
- [x] `@vue/cli-xxx` packages
- [x] `@vue/vue2-jest`
- [x] `eslint` + plugins
- [x] `ts-jest`
- [x] `typescript`
- [ ] any other lesser package updates (minor or patch version changes)
- [ ] change `import Vue from 'vue'` to `import { Vue } from 'vue-property-decorator'`
- [x] change `mixins: [...] to `Mixins(...)`
- [ ] related vue file updates
- [ ] fix property/method visibility in template, if time allows
- [ ] fix any broken unit tests

Acceptance criteria:
- `npm run lint` should not report any errors or warnings (with exceptions for some deprecated features)
- `npm run build` should not report any errors or warnings (with exceptions for some deprecated features)
- `npm run test:unit` should report all tests passing